U.S. Sen. Dick Durbin ruled himself out of the 2018 Illinois governor's race after keeping his Washington leadership post on Wednesday, leaving Illinois Democrats in a quandary as they look for someone to challenge Republican Gov. Bruce Rauner.

"I kept telling people of Illinois, I've got a pretty important job working in the United States Senate in the No. 2 Democratic position," said Durbin, who has been Senate whip for his party since 2005. "It was interesting to me that the day after the (Nov. 8) election, many of them came up to me and said, 'Stay in the Senate. We need you.'"

Durbin was the most buzzed-about potential Rauner challenger at July's Democratic National Convention, doing little then to quell the speculation. Since then, though, Durbin had been more dismissive of the idea, saying he was focused in Washington, where he hoped Democrats could take back the Senate from Republicans. That didn't happen, but Durbin survived talk of a challenge for his leadership position as Senate Democrats reorganized with the pending retirement of Senate Minority Leader Harry Reid of Nevada.

Durbin's decision leaves a wide-open race back home as Democrats look to defeat Rauner, the first-term Republican who previously has said he would seek re-election in two years.

The former private equity investor has spent tens of millions of dollars on his successful 2014 bid for governor and on this year's attempt to take away state House and Senate seats from Democrats. That could put a premium on a wealthy Democrat who could help fund his or her own bid, which some Democrats say could cost at least $40 million. The party estimates Rauner and his deep-pocketed allies could spend as much as $100 million.

At this early point, the Democratic field is in the name-floating stage.

Before the July convention, political operatives pushed the idea of a run by Chris Kennedy, son of the late Sen. Robert F. Kennedy and former chairman of the University of Illinois board of trustees. Addressing the Illinois delegation in July, Kennedy delivered a speech critical of Rauner. But afterward, Kennedy fled reporters questioning him about his potential interest in running for governor. Kennedy's name has been mentioned in the past for U.S. House, U.S. Senate and governor.

The name of J.B. Pritzker, a venture capitalist and co-founder and managing partner of the Pritzker Group, came up in a Wednesday Chicago Sun-Times bold-names column. A wealthy heir of the family that founded the Hyatt Hotel chain and a major Democratic donor, Pritzker did not respond to email for comment.

But multiple prominent Democrats, at the state Capitol for the legislature's fall session, said they were unaware of any interest by Pritzker, whose lone bid for office was a third-place finish in a 1998 primary bid for Congress.

In Springfield, talk has centered on a handful of names at this early point. As usual, there have been discussions about Attorney General Lisa Madigan, who last time ruled out a bid because her powerful father, Michael Madigan, remains the House speaker.

"I feel strongly that the state would not be well served by having a governor and speaker of the House from the same family and have never planned to run for governor if that would be the case," Lisa Madigan said in a July 2013 statement. "With Speaker Madigan planning to continue in office, I will not run for governor."

Since then, Rauner's Republicans have made a multimillion-dollar push to tarnish Michael Madigan's image in hundreds of commercials on behalf of GOP legislative candidates. That certainly doesn't help a Lisa Madigan bid, some Democrats say privately. In addition, there's no sign that Michael Madigan is leaving his legislative post anytime soon. To do so would look to Democratic allies as if he'd thrown in the towel against Rauner.

Beyond that, first-term Democratic state Treasurer Michael Frerichs of Champaign may be eyeing a bid, although his name recognition among voters is still somewhat low, some Democrats say.

Some state lawmakers also may be looking at the nomination, Democrats said. They include state Sens. Kwame Raoul of Chicago and Daniel Biss of Evanston. Raoul won re-election this month, and his Senate seat is not on the ballot in 2018. Biss, who orchestrated a multimillion-dollar federal super political action committee that worked to link Rauner to President-elect Donald Trump, would have to give up his Senate seat, which is up next election.

Also potentially looking at a bid is former Gov. Pat Quinn, whom Rauner vanquished in 2014. Quinn has been working to keep himself in the public eye by proposing ballot initiatives that include term limits for the Chicago mayor. But several leading Democrats are not enthused about the prospect of a return bid by Quinn.

As for Durbin, the 71-year-old from Springfield won a fourth six-year term in the Senate in 2014. If he chooses to run for a fifth term, the election would be in 2020.

A native of East St. Louis, Durbin was elected to the U.S. House in 1982 and served seven terms before winning election to the Senate in 1996. He is a graduate of Georgetown University's School of Foreign Service and the Georgetown University Law Center.

He cut his teeth on Capitol Hill as an intern in the office of Sen. Paul Douglas of Illinois. Another early job was as legal counsel to then-Illinois Lt. Gov. Paul Simon in the late 1960s and early '70s.

Durbin has been the party whip for U.S. Senate Democrats both when his party was in the majority and, as it is now, in the minority. He will work under Sen. Charles Schumer, D-N.Y., the next Senate minority leader.

After eight years of working with President Barack Obama, a close Durbin ally, Democratic senators are girding for the upcoming Trump administration.

Durbin's protege is Sen.-elect Tammy Duckworth, the U.S. representative from Hoffman Estates who on Nov. 8 captured the seat held by the state's junior senator, Republican Mark Kirk of Highland Park.